1. Field of the Invention
This invention relates to a heat exchanger for exchanging heat between fluids, which is effectively applicable to an intercooler for cooling the air (supercharged air) introduced into an internal combustion engine, for example, and is supercharged for combustion.
2. Description of the Related Art
The conventional heat exchanger, as shown in FIGS. 4, 5, is configured of a multiplicity of tubes 10 and a multiplicity of corrugated fins 11 stacked alternately with each other to make up a core unit 1. Also, tanks 2, 3 are arranged at the two ends in the longitudinal direction X of the tubes in the core unit 1, and side plates 4 are arranged at the two ends in the direction Y in which the tubes are stacked in the core unit 1.
This heat exchanger is assembled in such a manner that the component parts of the heat exchanger are assembled provisionally into a predetermined heat exchanger structure, after which the provisional assembly of the heat exchanger structure is fastened with wires from outside of the side plates 4 thereby to hold the state of the provisional assembly. Next, this provisional assembly is introduced into a brazing furnace and heated to the melting point of the brazing material thereby to braze the joints of the component parts of the assembly integrally with each other.
The side plates 4 have the function to hold the corrugated fins 11 located at the two ends in the stacking direction Y of the tubes and secure the brazed state between the corrugated fins 11 and the tubes 10.
In the case where this heat exchanger is used as an intercooler, and especially in a large diesel engine, a large temperature difference is generated between the tubes 10 and the side plates 4 due to the temperature of the supercharged air which has been increased to meet recently strengthened exhaust gas control requirements. The resulting difference of thermal expansion generates a large stress at the tube root (the joint between the tubes 10 and the tanks 2, 3) thereby often causing breakage of the tubes 10.
In view of this, the conventional heat exchanger has, in order to prevent the breakage of the tubes 10 due to the difference of thermal expansion, a slit 43 formed in the base portion 41 of each side plate 4 and a bent deforming portion 421 formed on each side wall portion 42 of the side plate 4 so that the side plates 4 are extended in accordance with the extension of the tubes 10 (for example, see the specification of European Patent Application Publication No. 1001241).
The conventional heat exchanger described above, however, has a gap between the base portion 41 and the bent deforming portion 421 in the direction Y in which the tubes are stacked. At the time of assembly before the integrating brazing process, therefore, the base portion 41 is liable to be displaced and the side plates 4 are easily twisted, thereby leading to the problem of buckling of the corrugated fins 11 and a dimensional error of the core unit assembly.